The field of this invention relates to prolonged release, ocular treatment for veterinary uses. It particularly pertains to the treatment of obstinate ocular infections, such as infectious bovine keratoconjunctivitis (IBK), or pinkeye, in cattle.
Known methods of treatment for infections such as IBK range from topical application of drops, ointments, or sprays to parenteral injection of a variety of antibiotics and sulfonamides.
A disadvantage of such treatment methods has been the difficulty of both obtaining and maintaining a therapeutic concentration of the drug in the tears and the affected tissues. One approach to the problem was reported by G. E. Hawley ("A New Treatment for Infectious Keratitis," North Am. Vet. 35: 507-509, July 1954). The tested procedure utilized an eye pellet that provided for a residual therapeutic concentration of terramycin in the tears for 31 hr.
A new form of prolonged release medication has been reported for use in treating glaucoma in humans (S. Lerman, "Prolonged Release Medication in the Treatment of Eye Disease," Isr. J. Med. Sci. 8: 1402-1405, Aug.-Sept. 1972). This device consists of an erodable matrix incorporating pilocarpine into a polymer so that the drug is released as the matrix dissolves. The structure of the device is relatively small as compared to the eye and is generally in the shape of a thin elliptical, solid body. It is designed for insertion into the ventral fornix of the conjunctival sac. However, in insertion tests performed on bovine eyes, the device floated in the tear film and frequently emerged from beneath the eyelid. Moreover, the nictitating membrane (third eyelid), which is not present in the human eye, caused the migration of the unit medially and propelled it onto the skin surface at the medial canthus. The units were retained for periods ranging from 5 min. to 2 hr.